One of the controlling factors in vesicle formation and trafficking are the mechanical properties of these vesicles. In this particular project we examine the assembly of clathrin triskelions into polyhedral coats of about 100-nanometer diameter which is believed to play a central role in receptor-mediated endocytosis and intracellular trafficking from the trans-Golgi network. Knowledge of the mechanical properties of the clathrin coat is needed in order to fully understand the function of the coat in the dynamical control of vesicle formation. The objective here is to measure the mechanical properties of clathrin-coated and uncoated vesicles in biological fluid environments. We have developed a scheme by which the nanomechanics of both vesicle types can be quantitatively explored by AFM, employing a deformation force in the 50-100 pN range.